1. Field of the Invention
The present invention relates to a musical tone control apparatus capable of accurately reproducing musical tones with noises generated from wind instruments, stringed instruments, and the like.
2. Prior art
One type of conventional apparatus known in the art is disclosed in Japanese Patent Application Laid-open No. 63-40199 and Japanese Patent Publication No. 58-58679.
According to the documents, FIG. 1 shows a construction of an apparatus for mixing musical tones, the construction being used for simulating the musical tones based on musical tone generation mechanism. In FIG. 1, reference numeral 11 denotes a ROM (read-only memory), 12 denotes an adder, 13 denotes a subtractive device, 14 and 15 denote multipliers. Accordingly, the construction is formed so that the operation of a mouthpiece and a reed for the clarinet is simulated when the clarinet playing. The above construction thus comprises an excitation circuit 10.
Reference numeral 20 denotes a bi-directional transmission circuit so that transmission characteristic of a resonance tube of the clarinet is simulated. Transmission circuit 20 comprises delay circuits D, D, ... for simulating transmission delay of air-pressure waves from the resonance tube; junctions JU, JU, ... intervened between delay circuits D, D, etc.; a low-pass filter LPF for simulating energy loss when the air-pressure waves reflect at the end portion of the resonance tube; and a high-pass filter for eliminating direct-current component of data which is transmitted into bi-directional transmission circuit 20. Junctions JU, JU, etc. are used for simulating scattering air-pressure wave at the various diameter of the resonance tube.
FIG. 1 also shows four multipliers M.sub.1 to M.sub.4, and two adders A.sub.1 and A.sub.2, these being of a lattice-type circuits. Symbols "1+K", "-K", "1-K", and "K" beside multipliers M.sub.1 to M.sub.4 represent multiplication constants, in which "K" is determined so that the transmission characteristic close to that of actual resonance tube is obtained.
According to the above construction, data P corresponding to a blowing pressure is supplied to adder 12 and subtractive device 13. Output data from adder 12 is then transmitted to delay circuit D, junction JU, delay circuit D, and the like, in bi-directional transmission circuit 20, and then transmitted to low-pass filter LPF. After transmitting it through low-pass filter LPF and high-pass filter HPF, output data from adder 12 is conversely transmitted to delay circuit D, Junction JU, and the like, then supplied to subtractive device 13 from bi-directional transmission circuit 20.
In addition, data P is subtracted from output data output from bi-directional transmission circuit 20 by subtractive device 13, in which the data corresponds to a pressure of the air-pressure wave which is returned to a gap between the mouthpiece and reed from the end portion of resonance tube. By virtue of the subtraction, data P.sub.1 corresponding to the air-pressure of the gap between the mouthpiece and reed is obtained. Supplying data P.sub.1 to ROM 11 generates data Y corresponds to "admittance", that is, it means a degree how air easily flows into the resonance tube, in other words, the data Y corresponding to a sectional area of the gap between the mouthpiece and reed from ROM 11.
FIG. 2 shows a characteristic of non-linear function "A" which represents the air-pressure of the gap between the mouthpiece and reed stored in ROM 11 related to the sectional area of the gap.
In addition, data Y is multiplied by data P.sub.1 in multiplier 14, so that data FL corresponding to a speed of air flow which is passed through the gap between the mouthpiece and reed is obtained. Data FL is then multiplied by multiplication constant G in multiplier 15, in which the multiplication constant G is a constant which is determined by various diameters of the instrument in the vicinity of the reed, i.e., the constant G expresses resistance to air flow in the vicinity of the reed, such as a "impedance". Accordingly, data P.sub.2 is obtained from multiplier 15, and represents a value which is multiplied the speed of the air flow passing through the gap between the mouthpiece and reed by the "impedance" against the air flow in the tube, that is, the data P.sub.2 represents a magnitude of pressure changes in the tube when air passing through the gap. Data P.sub.2 is then added to data P by adder 12, and then, the sum is supplied to bidirectional transmission circuit 20.
Accordingly, in a closed loop formed between excitation circuit 10 and bi-directional transmission circuit 20, data is circulated in the closed loop, that is, resonance operation is carried out. Data at the point of low-pass filter LPF in bi-directional transmission circuit 20 is then extracted from the apparatus, so that a musical tone is generated in accordance with the data.
On the other hand, in a wind instrument, when air blowing into the gap between the mouthpiece and the reed, a blowing noise is generated from the gap, thereby mixing the blowing noise with the data.
Conventionally, mixing the blowing noise and the data has been carried out so as to overlap data P corresponding to the blowing pressure with data corresponding to the blowing noise.
FIG. 3 shows an apparatus for mixing musical tones generated from both stringed and percussion instruments. In FIG. 3, reference numeral 101 denotes a ROM for storing an initial wave form, for example, first one-cycle of an immediately after musical tone which is generated from the stringed or percussion instrument. Reference numeral 102 denotes a delay circuit, 103 denotes a selection circuit, and 104 denotes a filter.
The apparatus for mixing musical tones begins operating in accordance with a musical tone generation instruction output from a musical tone generation instructor (not shown). When the apparatus receives the musical tone generation instruction outputted from the musical tone generation instructor, selection circuit 103 transmits one-cycle of wave data from ROM 103 to an output portion, and to filter 104. Also, the one-cycle wave data in which the band-width is limited by filter 104, is supplied to delay circuit 102. Afterwards, the one-cycle wave data is circulated in the circuits in the order of selection circuit 103, filter 104, and delay circuit 102, and is transmitted to the output portion at every circulation. According to the above construction, musical tones are mixed with each other so that tone colors are changed in accordance with the elapsed time when the stringed and percussion instruments are played.
When the stringed and percussion instruments are played, it is known that noise overlap with each of the musical tones in the beginning of play in case of the stringed instrument, and also in case of hitting the percussion instrument. However, the conventional apparatus for mixing musical tones does not generate such noise.
According to the above-mentioned, the method for reproducing noises in which the noise overlaps data corresponding to the blowing pressure of the wind instrument is not suitable for the generation of actual noise, in other words, the noise is not natural.